Operational failures by the Great Lakes Water Authority were not a significant cause of flooding in and around Detroit last June, according to a new independent report commissioned by the GLWA.
An overnight storm in the early morning hours of June 26 dumped more than six inches of rain in just a few hours. The result was widespread surface flooding and basement back-ups, particularly in parts of Detroit, the Grosse Pointes, and Dearborn.
After the storm, it was revealed that a power failure at a pumping station on Detroit’s east side kept some pumps from working and others from coming online. But according to the report, while the pumping failures likely “exacerbated” the flooding, it was the sheer amount of rainfall in such a short period of time that overwhelmed the sewer system.
These facts suggest "that conveyance capacity in the collection system, not pumping, was the primary cause of flood risk, and additional pumping capacity would not have appreciably reduced the risk of basement backups,” the report states. “Rather, a strategic assessment of conveyance improvements, inlet controls and in-system storage is warranted.”
The GLWA, which faces multiple lawsuits and thousands of claims as a result of the flooding, is using the findings as evidence that the events were the “inevitable” result of the kind of intense storms driven by climate change.
“The unprecedented rain events of last summer are a real-life example of the devastating impacts that climate change can have on our communities,” GLWA Interim Director Suzanne Coffey said in a statement. “It is likely that we will continue to see more intense storms at a greater frequency. While it is not possible to eliminate the chance of flooding given these circumstances, we are taking actions that can help mitigate the extent of the flooding.”
The report contains short and long-term recommendations for adapting water and sewer infrastructure to that new reality. Those recommendations range from constant preparation for intense storms and upgraded pumping infrastructure, to re-designing system capacity for a higher level of flood protection.
In a statement, GLWA said it’s also “begun working with its legislators to identify funding at the federal level for a Flood Risk Mitigation Study for southeast Michigan. The comprehensive feasibility study, which will be conducted in partnership with the Army Corps of Engineers, would evaluate the implementation of concepts such as wastewater storage at grade or deep tunnel levels, using pumping stations for discharge, constructing large diameter relief sewers, and strategic sewer separation to address the long-term impacts of climate change."
